exchange 2013 and outlook 2013.

exchange user sending attachments to email accounts outside company, MSN and AT&T email accounts.

occasionly they are receiving the winmail.dat file instead of the attachment.  have tried changing his outlook and adress book settings, but they may be getting changed back somehow.

is there a GPO that can be applied to outlook 2013 that will block the ability to send email via RTF format?

I recommend that you post this in the Outlook Forum:  http://social.technet.microsoft.com/Forums/en-US/outlook/threads

Hi,

Check this KB 138053

https://support.microsoft.com/en-us/kb/138053

And run this command to have a test.

Set-RemoteDomain -Identity <Name of Domain> -TNEFEnabled $false

Best Regards.